1. Field of the Invention
This invention relates generally to an electronically controlled high resolution light source, and more particularly, to a thin film electroluminescent .edge emitter structure arranged to provide a linear array of individual light-emitting pixels and positioned on a silicon substrate having formed therein an electronic power-switching network which is operable to control the illumination of the various pixels forming the array.
2. Background Information
The use of electronically controlled, high resolution light sources is well known. For example, light-activated printers capable of high resolution (e.g. 240 to 1000 dots per inch) are presently available which utilize a laser as the high resolution light source. Such printers are more versatile than impact printers and can, for instance, print different type styles and sizes at any time, under electronic control.
It is also known to utilize electroluminescent devices in various flat panel display devices. An example of this type of application is disclosed in U.S. Pat. No. 4,110,664 to Asars et al. which is assigned to the assignee of the present invention. The flat panel display device of the above-identified patent is an electroluminescent bar graph display system which includes, on a unitary substrate, a plurality of discrete, individually controllable adjacent electroluminescent display elements interconnected to a thin film transistor dynamic shift register. Individual stages of the shift register are connected to individual display elements. The electroluminescent display element utilized in such a system is of the type in which one of the electrodes for use with the electroluminescent phosphor is a common light transmissive member. This common electrode is contiguous with the device face and the emissions must pass through this electrode.
The structure of such a display panel may also be seen in U.S. Pat. No. 4,006,383 to Luo et al. which is also assigned to the assignee of the present invention. The Luo et al. patent discloses an electroluminescent display panel structure in which individual electroluminescent electrodes cover a large are of .the panel in order to increase the active display area. The face of the electroluminescent element is the display surface electrode.
Another example of an electronically controlled, high resolution light source is disclosed in U.S. Pat. No. 4,535,341 to Kun et al., which is assigned to the assignee of the present invention. This patent discloses a thin film electroluminescent line array emitter structure which provides edge emissions which are typically 30 to 40 times brighter than the face emissions of conventional flat panel display light sources. In one embodiment of the invention, the emitter structure includes an integral capacitor in series with each emitter structure pixel. This integral thin film structure dielectric and phosphor composite layer serves as both the light-emitting layer for the edge emitting device and the dielectric for the capacitor.
While the prior art discloses various thin film electroluminescent flat panel and edge emitter devices, there is a need for a thin film electroluminescent (TFEL) edge emitter structure which is disposed on a layer of substrate material and connected with one or more integrated circuits formed in the substrate layer. The thin film electroluminescent (TFEL) edge emitter structure and substrate layer form a thin film electroluminescent (TFEL) edge emitter assembly wherein the integrated circuits provide a power-switching function to control the illumination of the individual pixels of the TFEL structure. Forming the pixel illumination control circuitry within the substrate layer eliminates the need for an external pixel illumination control system; thus providing a thin film electroluminescent edge emitter assembly which is both inexpensive and relatively easy to manufacture.